Today many electronic systems, including computer systems, physically consist of several circuit boards, or cards, that plug into a common “backplane” circuit board. The circuit boards are usually multi-layer printed circuit (“PC”) boards with discrete and integrated components that are soldered or otherwise physically attached to and-in contact with “traces” which are conducting paths connecting the devices to form the electronic circuit. The backplane is usually another PC board with sockets to hold the multiple circuit boards, and which has conducting paths connecting the pins in the sockets, and thus the circuitry on the circuit boards with one another. The assembly of circuit boards that plug into a backplane is often held in an equipment shelf that uses slots or rails to guide the circuit boards and keep each aligned with its associated socket on the backplane during insertion or removal.
One of the problems with this configuration is that the backplane traces and thus the connections between the circuit boards are fixed in hardware. Once the backplane has been designed, there are limits on the types of changes that can be made to the signal paths between the circuit boards. If the system designer desires additional bandwidth or types of connectivity between circuit boards, and these additional accommodations are not supported by the backplane configuration, the designer must resort to additional hardware or to redesigning the backplane to satisfy the new need. Such remedies may include a fiber-optic link between the circuit boards, paddleboards that connect to wire-wrap pins on the reverse side of the backplane, or ribbon cables that connect to sockets on the edges of the boards.
Redesigning the backplane is undesirable because it increases the number of proprietary-specific backplane configurations thus reducing circuit board interchangeability. Specialized backplanes require specialized boards to fit those backplanes, and this means that neither the backplane nor the boards themselves can be purchased “off the shelf” from third party vendors. Redesigining hardware also slows the product development cycle and increases the time between product concept and market availability.
Adding hardware links between circuit boards in a shelf makes assembly and maintenance-of the finished product much more complex. In order to replace a board in a shelf, all connections must be removed before the circuit board itself can be removed. The connectors between the circuit boards add additional points of failure, and reduce the reliability of the boards and thus the system. Replacing a faulty circuit board in the shelf takes longer when there are cables or fibers connected to the board that must be manipulated, increasing the time required to repair a fault. And sometimes the links between circuit boards may be “daisy chained” so that removing the link from any board may isolate other unrelated boards from one another.
If a specific hardware link is created between circuit boards, either through conductors in the backplane or using cables or fibers connecting the boards, the characteristics of that link become quite fixed in nature. It is generally difficult to change the type of data, bandwidth, or function of a hardware link simply because the hardware is designed to provide a path for a very specific type of data, bandwidth, or function. The hardware connection thus typically reduces the flexibility of the design of the circuit board and the system. As an example, if a two-conductor Ethernet connection is provided between two circuit boards in an existing configuration, it is very difficult to redesign the hardware connection to instead provide a high-speed mate-update bus between the two circuit boards. An additional hardware path would be needed to provide this function. Thus, the physical parameters and characteristics of a circuit board connection affects the functions available in that connection.
What is needed is a generic, flexible connection technology between circuit boards in a backplane that provides a data path between the boards, which is independent of the backplane, and which requires no physical connection between the boards. Accordingly, it is the object of the present invention to provide a data path between circuit boards in a backplane with these characteristics.